Mosul is liberated, a fallen policewoman is mourned, and Donald Trump Jr. is exposed.

Three important things happened this week. Two were insufficiently noted.

Iraq’s second-largest city, Mosul, fallen three years ago to Islamic State, was liberated by forces of the Iraqi government. Not long ago ISIS, the first and true sustained scum of the 21st century, was seen as militarily formidable and ideologically perhaps indomitable. Now they’ve disappeared into the hills. The fall of Mosul is a blow to their mystique, and that of radical Islam. As for the Iraqi military, not long ago it was derided as...